Knives out for Mike Waltz as Donald Trump fires national security officials

Donald Trump’s national security adviser was already on thin ice after the “Signalgate” affair. When the US president sacked important members of his staff on Thursday, the ice sprang a whole new set of cracks.

Mike Waltz has been in the spotlight since he created a group chat on the messaging app Signal to discuss sensitive information about a US strike on Houthi rebels in Yemen, and accidentally invited a journalist to join it.

Trump has refused to sack him over the incident. But the…